FXUS66 KSGX 242141
AFDSGX

Area Forecast Discussion
National Weather Service San Diego CA
241 PM PDT Fri May 24 2019

.SYNOPSIS...
Except for a slight chance of showers near the San Bernardino 
Mountains this afternoon and Saturday afternoon, it will be drier 
and warmer through Saturday. For Sunday into Monday, a low pressure 
system from the north will bring cooling, stronger onshore flow with 
strong and gusty southwest to west winds in the mountains and 
deserts for Sunday into Sunday night, and periods of showers for 
Sunday into Monday morning. Tuesday through Thursday will be dry 
with a warming trend, but with temperatures remaining below normal
through next week.

&&

.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...

Moderate cumulus over the mountains this afternoon but no showers
have developed in our local mountains at this time, although there
are a few showers over nearby mountains and the Mojave Desert. Our
region will continue to experience fair weather conditions through
Saturday evening, under control of a baggy long wave trough over 
the SW region. By Saturday night, an upper level low pressure
system will have dropped from the Gulf Of Alaska into Central
California, quite strong and cold for this time of the year,
strengthening into a 544 DM upper low near San Francisco by
Saturday night. 

Most of our model guidance is in agreement that the upper level 
low will take a beeline across Central California Sunday through 
Sunday evening, with the best lift and cold air tracking just 
north of our area across the Southern Sierra and Mojave Desert. As
has been the case with the last several storm systems, the 
guidance has been slowly nudging further south with each run, and 
since yesterday the consensus track has dropped a bit further 
south, but still just to the north of our region. Sunday night 
through Monday night, the upper level storm will gradually fill in
as the system ejects to the NE around the periphery of the large 
upper ridge across the SE USA. 

Even with the track differences in the forecast with some run to 
run differences, we are still expecting an episode of widespread 
but mainly light rain across our area, focused on Sunday afternoon
and evening. Snow levels will be the lowest across our San 
Bernardino Mountains, and may require another late season winter 
weather advisory above about 6000-6500 feet, where a few inches of
new snow will be possible. Rainfall amounts for the coast and 
valleys will mainly be around one-tenth of an inch, with a few 
spots around one- quarter of an inch, and up to one inch in the 
favorable upslope (coastal slopes) of the San Bernardino and Riv 
CO Mountains. 

Onshore winds across the mountains and deserts will become strong
Saturday night, peaking Sunday and Sunday night when we will
likely need a wind advisory for the passes and along the desert
slopes. Little precipitation is expected in the deserts,
especially in the lower deserts and Coachella Valley, where the
biggest concern will be from the persistent gusty winds and
potential for airborne dust and sand problems. 

Amazingly the baggy trough pattern looks to continue through much
of next week, with temperatures struggling to get even close to
normal levels for this time of the year (near 100 degrees in the
Coachella Valley for example). The GEFS and ECM ensemble means
favor the baggy trough for much of next week. Most models then
begin to introduce a strengthening East Pac ridge by next weekend,
which would finally bring a break to all of the active weather
that SoCal has been experienced, with the potential for above
normal temperatures, well perhaps beyond next week! 


&&

.AVIATION...
241950Z...Coast/Valleys...FEW low clouds with bases 1500-2500 feet 
MSL this afternoon/evening. Increasing coverage of low clouds after 
03Z in the coastal basin with bases around 1500 feet MSL...spreading 
up to 20 miles inland by 14Z Sat. 

Mountains/Deserts...SCT-BKN clouds with bases around 6000 ft MSL and 
unrestricted vis this afternoon. Higher terrain obscured in 
clouds/fog at times. Mostly clear overnight.

&&

.MARINE... 
No hazardous marine weather is expected through Wednesday.


&&

.SKYWARN... 
Skywarn activation is not requested. However weather spotters are
 encouraged to report significant weather conditions.


&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.
&&

$$

PUBLIC...Brotherton
AVIATION/MARINE...PG